Considerable and considerate 相当大的与考虑周到的

Once I went on an outing with one of my American friends together. On the way he looked after me very carefully. I was very grateful to him in my heart. Besides saying "thank you", I also added, "You're so considerable." In fact I meant to praise him for being thoughtful. However, as soon as I uttered that, my friend, previously wearing a bright facial expression, then quickly took on a ghastly (难看的，可怕的）look. I immediately perceived something wrong, but I did not know where my mistake laid and I felt very embarrassed.

Fortunately, my friend was really good at understanding others. He hesitated and said, "I think you wanted to say I'm considerate." I hastened to ask him about the differences between the two words.

It turns out that "considerable" means" rather large in size, etc. or of noticeable importance", （and my friend happened to be an extremely burly （大块头的）man, which he was sensitive to) while "considerate" was what I wanted to express.

It is really true that an error in the breadth of a single hair can lead you a thousand li astray（失之毫厘，差之千里）